The perpetuation of rheumatoid synovitis will be studied in the context of an autologous mixed lymphocyte reaction (AMLR) model. We have recently observed a similarity between the lymphokines produced in the AMLR and in the rheumatoid joint: Both show IL-3 like activity (defined by mast cell growth factor (MCGF), colony stimulating factor (CSF), and stimulation of IL-3 dependent cell lines) and both contain low amounts of IL-2 and IFN-gamma. The relatively restricted lymphokine profiles of these two situations suggest that they may share a similar pathogenesis. Studies of lymphokines secreted into synovial fluid or into medium in an AMLR are complicated by the presence of inhibitors, local degradation, and absorption. Therefore, we propose to study the production of lymphokines in these two systems at the mRNA level. Messenger RNA levels of various cytokines in RA synovium and in AMLR cells will be measured using riboprobe protection assays. In addition, in situ hybridization will be performed on AMLR cells and tissue sections of rheumatoid synovium to determine the phenotype and local environment of cytokine secreting cells in the joint. These studies will also be extended to other forms of chronic inflammatory arthritis. In addition, the unique IL-3 like activity produced in the inflamed joint will be characterized. Preliminary data has already shown that at least two factors are responsible for the activity (i.e. MCGF and CSF), and that these factors are distinct from IL -3. We plan to identify and clone those activities from a human synovial cDNA library.